Metastatic malignant melanoma from anorectum presenting as an isolated breast tumor: A case report and literature review

Rationale: Anorectal malignant melanoma regularly exhibits a biological aggressive behavior which is metastasizing to lung, bone, brain or other organs and tissues early in the course of the disease. Compared with melanoma in the other parts of the body, anorectal malignant melanoma is relatively rare. Metastatic to the breast tissue from anorectal malignant melanoma or from other extra-mammary tumors are very rare. Patient concerns: We report the case of a 65-year-old female who suffering from anorectal malignant melanoma and implemented complete surgical resection. Two years later, a space-occupying lesion in the outer upper quadrant of the right breast was observed on a chest CT. Diagnosis: The right breast was excised, and breast metastasis of anorectal malignant melanoma was histologically confirmed. Interventions: Radical mastectomy of the right breast was performed, and no lymph nodes or other metastases were observed. Outcomes: The patient's operative course was uneventful. The patient completely recovered and transfers to the oncology department for further treatment. Lesson: The patient presented with an isolated breast tumor. Duo to Malignant melanoma could mimic many kind of poorly differentiated tumors, it is difficult to diagnose accurately, especially when it appears as an isolated mammary tumor. Because of the treatment measures and prognosis between malignant melanoma and breast cancer are entirely different.